mediator.md

Mediator Design Pattern

The Mediator Pattern facilitates communication between objects, promoting loose coupling by preventing them from referring to each other directly. Instead, objects interact through a mediator.

How to apply

interface Mediator
{
    public function notify(string $event): void;
}

class BookStoreMediator implements Mediator
{
    public function notify(string $event): void
    {
        echo $event;
    }
}

abstract class Party
{
    public function __construct(protected Mediator $mediator) {}
    abstract public function send(string $event): void;
}

class Buyer extends Party
{
    public function send(string $event): void
    {
        $this->mediator->notify("Buying: {$event}");
    }
}

class Seller extends Party
{
    public function send(string $event): void
    {
        $this->mediator->notify("Selling: {$event}");
    }
}

Usage:

$mediator = new BookStoreMediator();

$buyer = new Buyer($mediator);
$seller = new Seller($mediator);

$buyer->send("Lord of the Rings");
$seller->send("The Hobbit");

Output:

Buying: Lord of the Rings
Selling: The Hobbit